The effect of angiotensin II on the basal and K+-evoked release of [3H]norepinephrine was examined in hypothalamic and brainstem synaptosomes from adult male normotensive (Wistar-Kyoto, WKY, and Sprague-Dawley, SD), and spontaneously hypertensive (SH) rats. Angiotensin II attenuated the [3H]norepinephrine release caused by maximal depolarizing concentrations of K+ (75 mM) in hypothalamic synaptosomes of the SH rat, but had no effect on basal [3H]norepinephrine release. Angiotensin II had no effect on either the basal or K+-evoked release of [3H]norepinephrine in brain synaptosomes prepared from either WKY or SD adult male rats. The results suggest a distinct role of angiotensin II in the modulation of catecholamine release in the SH rat.